Crosslinkable composition of matter III

ABSTRACT

A novel composition of matter is provided, which comprises certain polydiene-functionalized polyisocyanate oligomer and certain polydieneophile-functionalized epoxy-amine adduct, which polyisocyanate oligomer and epoxy-amine adduct are reactive at elevated cure temperature. The polydieneophile-functionalized epoxy-amine adduct comprises the reaction product of certain polyhydroxy functional epoxy-amine reactant with dieneophile functional mono-isocyanate reactant. The polydiene-functionalized polyisocyanate oligomer comprises the reaction product of polyisocyanate reactant, preferably a triisocyanate, with approximately equal molar equivalent amount of monohydroxy diene reactant or monoamino diene reactant or like isocyanate-reactive diene reactant. The crosslinkable composition of matter is useful in coating and other applications, especially cathodic electrocoating applications.

TECHNICAL FIELD

This invention relates to a composition of matter comprising certaindiene-functionalized polyisocyanate oligomers together with certaindieneophile-functionalized epoxy-amine adducts, which adducts arereactive with the oligomers at elevated cure temperatures. According tocertain preferred embodiments, this invention relates to use of suchcrosslinking compositions of matter to prevent corrosion of corrosionsusceptible substrates such as ferris metal substrates and the like.This invention especially relates to aqueous coating compositionscomprising such dieneophile-functionalized epoxy-amine adducts anddiene-functionalized polyisocyanate oligomers, with aqueous coatingcompositions are adapted for use in cathodic electrodepositionprocesses.

RELATED APPLICATIONS

This application is related to concurrently filed application Ser. Nos.455,678, 455,718, 455,719, 456,067 and 456,068.

BACKGROUND ART

Coating compositions are known which are suitable for application to asubstrate, for example, by spraying, dipping, electrodeposition or thelike, which coating compositions are then cured by baking the coatedsubstrate at an elevated temperature. Typically, such coatingcompositions comprise resinous materials or blends of resinousmaterials, in some cases together with suitable crosslinking agentreactive with such resinous materials at elevated temperature.

In regard to electrodeposition of coatings, the process is welldescribed in the art. Typically, an aqueous bath containing the coatingcomposition is placed in contact with an electrically conductive anodeand an electrically conductive cathode, and upon the passage of electriccurrent (normally direct current) between the anode and the cathode, anadherent film of the coating composition is deposited. Depending uponthe nature of the coating composition, the coating may be deposited atthe anode or at the cathode. The process parameters vary widely. Thevoltage applied may vary from as low as, for example, one volt to ashigh as, for example, 500 volts or higher. Typically, however, thevoltage used ranges from about 50 to about 400 volts.

A wide variety of electrodepositable resins are known to the skilled ofthe art. For example, a number of water-soluble, water-dispersable, orwater-emulsifiable polycarboxylic acid resins can be electrodeposited.Some of these resins include, for example, reaction products or adductsof a drying oil or semi-drying oil fatty acid ester with a dicarboxylicacid or anhydride; interpolymers of a hydroxyalkyl ester of anunsaturated carboxylic acid, unsaturated carboxylic acid, and at leastone other ethylenically unsaturated monomer; alkyd-amine vehicles, thatis vehicles containing an alkyd resin and an amine-aldehyde resin; andmixed esters of resinous polyols. In U.S. Pat. No. 3,991,028 to Irwin etal, electrodepositable compositions are disclosed which comprise awater-dispersion of a hydrolyzed polyepoxide in combination with aninterpolymer of a hydroxyalkyl ester, an unsaturated acid and at leastone other monomer, and an amine-aldehyde resin. The use of a hydrolyzedpolyepoxide is said to provide improved properties and to avoidagglomeration of the coating composition. In U.S. Pat. No. 4,026,855 toParekh et al, a coating composition is disclosed to be adaptable for usein electrodeposition or as a water-based coating for application byspray or dip coating methods. The composition comprises an aqueousdispersion of (A) an ungelled modified crosslinking agent comprisingcertain aminoplast crosslinking agent modified by reaction with anon-resinous compound containing hydroxy-group containing carboxylicacid, and (B) a water-dispersable non-gelled polymeric material carryinga cationic charge and containing at least one class of reactive groupsselected from carboxyl groups, alcoholic hydroxy groups and amide groupsand also containing amino groups, and (C) an acid solubilizer. In U.S.Pat. No. 4,033,917 to Sekmakas et al, certain copolymers ofpolyethylenically unsaturated epoxy-amine adducts are disclosed and alsostable aqueous dispersions containing same and also theelectrodeposition of such aqueous dispersions at the cathode of aunidirectional electrical system. Specifically, amine functionalpolymers dispersable in water with the aid of a solubilizing acid aresaid to be provided by copolymerizing (A) certain ethylenicallyunsaturated hydroxy functional amine adduct free of epoxy groups; and(B) copolymerizable monoethylenically unsaturated monomers, a portion ofwhich is amine-functional. The copolymer is said to be stablydispersable in water at certain pH and to be electrodepositable at thecathode, optionally together with an aminoplast curing agent to providecoatings which can be cured, usually by exposure to elevatedtemperature. U.S. Pat. No. 3,471,388 to Koral is directed to a cathodicelectrocoating composition which incorporates an aminoplast crosslinker(e.g., butylated melamine) with an aminated polymer containing hydroxygroups. Numerous suitable hydroxy-containing aminated polymers aresuggested which have capability to crosslink with an aminoplastcrosslinking agent. One such suggested polymer is the reaction productof a poly-functional amine with a poly-functional epoxy compound. Thepolyhydroxy polymers are said to be dispersable in water upon additionof suitable acid such as acetic acid.

Additional teaching directed to coating compositions suitable for use inelectrocoating processes is provided in U.S. Pat. No. 4,159,233 to Tingeet al; U.S. Pat. No. 4,057,523 to Blank; U.S. Pat. No. 4,182,831 toHicks; U.S. Pat. No. 4,192,932 to Dickie, which patent is assigned tothe assignee of the present application; U.S. Pat. No. 4,192,929 toBloomfield, which patent is assigned to the assignee of the presentapplication; U.S. Pat. No. 4,202,746 to Lee et al; and U.S. Pat. No.4,072,536 to Otsuki et al.

It is a general objective of the present invention to provide certainself-crosslinkable epoxy-amine adduct adaptable for use in coatingcompositions, including coating compositions adapted for use inelectrodeposition processes, and also for use in the manufacture of lowpressure laminates, adhesives, molding compounds and textile treatingresins. It is a further objective of the invention to providesolvent-based coating compositions and water-based coating compositionsapplicable to a substrate by spray or dip coating or the like.

One particular objective of the invention is to provide aself-crosslinkable coating composition comprising an aqueous dispersionof self-crosslinkable epoxy-amine adduct, which coating composition isadapted for use in the electrodeposition of coatings onto electricallyconductive substrates, in particular, crosslinkable coating compositionsadapted for use in the cathodic electrodeposition of coatings,especially corrosion resistent primer coatings on automotive vehiclebody panels. Additional objects and aspects of the present inventionwill be apparent from the following description thereof.

DISCLOSURE OF THE INVENTION

The present invention provides a novel crosslinkable composition ofmatter, which composition comprises:

A. substantially gel-free dieneophile-functionalized epoxy-amine adduct,preferably of number average molecular weight about 500-7000, comprisingthe reaction product of (i) polyhydroxy functional epoxy-amine reactantcomprising the reaction product of polyepoxy reactant having an averageof at least about 2 epoxy groups per molecule with secondary aminereactant having a total of less than about 20 carbons per aminonitrogen, wherein each hydroxy group, if any, of the secondary amine isremoved at least 1 carbon from each amino nitrogen, with (ii)dieneophile functional mono-isocyanate reactant; and

B. substantially gel-free, substantially isocyanate-freediene-functionalized polyisocyanate oligomer, preferably of numberaverage molecular weight about 450-7000, having number average dienefunctionality of at least about three, comprising the reaction productof (i) polyisocyanate reactant, preferably a triisocyanate, with (ii)mono-hydroxy, mono-amino or like isocyanate-reactive diene functionalreactant, wherein the polyisocyanate reactant and the diene functionalreactant are reacted in molar equivalent ratio of one to at least aboutone, respectively.

The crosslinkable composition of the invention is particularly useful incoating compositions and according to one preferred embodiment furtherdiscussed below can be adapted for use in electrodeposition coatingprocesses. Crosslinkable compositions provided by the invention may alsobe used in the manufacture of low pressure laminates, adhesives, moldingcompounds and textile treating resins. According to a significantlyadvantageous aspect of the invention, the cure rate and storagestability of the crosslinkable, heat curable composition is readilycontrollable, as further described below, through selection of suitablediene and dieneophile resin structure. In addition, the crosslinkdensity in the cured composition can be easily and precisely controlledby suitable selection of epoxy amine resin or by varying thestoichiometry of the reaction between the epoxy amine resin and thedieneophile-functional mono-isocyanate reactant used to make thedieneophile-functionalized epoxy-amine adduct or by varying theisocyanate equivalent weight of the polyisocyanate reactant used to makethe diene-functionalized polyisocyanate oligomer.

In regard to coating compositions, the crosslinkable compositions of thepresent invention are particularly adaptable for use in processes forthe cathodic electrodeposition of heat curable coatings, especiallyhighly alkali resistant primer coatings on automotive vehicle bodypanels. In such application the coatings provided by the invention arefound to be highly resistant to solvents and humidity and to provideexceptional corrosion protection for the underlying substrate. Theinvention is particularly advantageous in that the novel cure chemistryallows for low temperature curing of the coating. Such crosslinkablecomposition of the invention comprises:

A. substantially gel-free dieneophile-functional epoxy-amine adduct, atleast partially neutralized with a solubilizing acid, typically anorganic acid such as, for example, acetic acid or the like, whichdieneophile-functionalized adduct comprises the reaction product of:

(i) polyhydroxy functional epoxy-amine reactant, preferably of numberaverage molecular weight about 300-10,000, comprising the reactionproduct of polyepoxide reactant having an average of at least about twoepoxy groups per molecule with secondary amine reactant having a totalof less than about 20 carbons per amino nitrogen, wherein each hydroxygroup, if any, of the secondary amine is removed at least 1 carbon fromeach amino nitrogen, such as, for example, diethanolamine, with

(ii) dieneophile-functional mono-isocyanate reactant; and

B. substantially gel-free substantially isocyanate-freediene-functionalized polyisocyanate oligomer having number average dienefunctionality of at least about three, comprising the reaction productof

(i) polyisocyanate reactant, preferably of number average molecularweight about 200-3000, having more than two isocyanate functionality permolecule, with

(ii) mono-hydroxy, mono-amino or like isocyanate reactive dienefunctional reactant, wherein the polyisocyanate reactant and the dienefunctional reactant are reacted in molar equivalent ratio of one to atleast about one, respectively,

which at least partially neutralized dieneophile-functionalizedepoxy-amine adduct and diene-functionalized polyisocyanate oligomer aredispersed in aqueous solvent.

Such coating composition will deposit a heat curable coating at thecathode in an electrodeposition coating process according to techniqueswell known to the skilled in the art. Other features and advantages ofthe present invention will become more apparent from the followingdetailed description including the preferred embodiments and best modeof the invention.

DETAILED DESCRIPTION OF THE INVENTION Dieneophile-FunctionalizedEpoxy-Amine Adduct

The first essential component of the crosslinkable composition of theinvention is the dieneophile-functionalized epoxy-amine adduct. Thiscomponent comprises the reaction product of certain polyhydroxyfunctional epoxy-amine reactant with dieneophile functionalmono-isocyanate reactant. The polyhydroxy epoxy-amine reactant can beformed in non-aqueous medium by reacting any of certain secondary amineswith a di- or polyepoxide, that is, a polyepoxide having an average ofat least about two epoxy groups per molecule. The polyepoxide ispreferably free of carboxy ester moieties linking the epoxide groups,since such carboxy ester-free polyepoxides have been found to providecured coatings according to the invention which are significantly morealkali resistant and provide significantly enhanced corrosion protectionto the underlying substrate.

One class of suitable polyepoxides includes the the reaction products ofdi- or polyhydric, mono-, di- or polycyclic compounds withepihalohydrins of the formula ##STR1## wherein X is halogen such aschloro and Y is hydrogen or lower alkyl such as, for example, methyl orethyl, which epihalohydrin reaction products are exemplified by straightchain epoxy terminated compounds containing glycidyl ether groups suchas bis-phenol A-epichlorohydrin reaction products. These arecommercially available as, for example, Epon 828, 1001 or 1004(trademarks) marketed by Shell Chemical Company, Houston, Tex., U.S.A.Such products contain aromatic groups, such as benzene nuclei at apreferred average of at least about one, more preferably for thisinvention at least about two, for each terminal epoxy group. Especiallysuitable are bis-phenol A epichlorohydrin reaction products comprisingin major amounts up to 10 or more bis-phenol moieties within theepichlorohydrin reaction product backbone, for example, those of numberaverage molecular weight up to about 8000, preferably 700-6000.

Other suitable polyepoxides include, for example, the Novolac epoxyresins, e.g. Epon 152 and 154 (trademarks) marketed by Shell ChemicalCompany, Houston, Tex., U.S.A. These polyepoxy resins include epoxidizedproducts of phenol formaldehyde resins that contain terminal glycidylether groups from aromatic moieties.

Aliphatic, including cycloaliphatic, epoxy compounds having, on theaverage, at least about two epoxy groups per molecule may also beemployed. Such aliphatic epoxy compounds include epihalohydrin andaliphatic di- or polyols such as glycol reaction products, epoxidizedpolybutadienes, vinylcyclohexenedioxide and dipentene dioxide. Stillfurther, hydrogenated bis-phenol A epichlorohydrin products may also beemployed.

In one preferred embodiment, the polyepoxide comprises relatively highmolecular weight (e.g. number average above about 700) epoxy compoundhaving hydrophobic groups such as, for example, the reaction product ofepihalohydrin with diol, e.g. bis-phenol A. These have been found toadvantageously provide enhanced moisture resistance to the curedcoatings as compared to lower molecular weight epoxy compounds made inthis way. Alternatively, as will be more fully described hereinafter,certain lower molecular weight epoxy compounds may be reacted withsecondary alkanolamines to provide epoxy amine reaction products thatsimilarly provide enhanced moisture resistance. Preferably, however, theepoxy reactant comprises higher molecular weight epoxy compounds such asthose bis-phenol A-epichlorohydrin reaction products having at leastabout 25 mole percent, more preferably at least about 75 mole percent,constituent compounds that have two or more, preferably about 3-10aromatic groups per epoxy group.

Numerous additional suitable polyepoxide materials are commerciallyavailable or readily prepared using well known techniques andcommercially available starting materials, and these will be apparent tothe skilled of the art in view of the present disclosure. Compatiblemixtures of any of these epoxy compounds also are suitable.

The amine reactant preferably comprises secondary amine having a totalof up to about 20 carbons per amine nitrogen. More preferably at leastabout 75 mole percent of the amine reactant comprises at least one andpreferably two primary hydroxyl groups, each hydroxyl group on a carbonatom at least one carbon removed from any amino nitrogen. Preferredsecondary amine reactants include, for example, dialkylamine,dialkanolamine, N-alkylaniline and the like and a compatible mixture ofany of them, wherein each alkyl moiety and each alkanol moiety has fromone to about ten carbons, more preferably one to about six carbons. Mostpreferred are the lower dialkanolamines, especially diethanolamine, inview of their ready commercial availability, low cost, and ease ofreaction with the preferred polyepoxides. While not wishing to be boundby theory, it will be understood by the skilled in the art that theamine/epoxide reaction generates an hydroxyl group in the epoxy-amineadduct reaction product. Each such hydroxyl group of the epoxy-aminereaction product can react with an isocyanate functionality of thedieneophile functional mono-isocyanate reactant. In addition, eachhydroxyl functionality contributed to the epoxy-amine adduct by analkanol moiety of the secondary amine will be available for reactionwith the dieneophile functional mono-isocyanate reactant. Accordingly,it will be understood that, as one significant advantage of the presentinvention, the degree of dieneophile functionalization of thedieneophile-functionalized epoxy-amine adduct can be controlled to alarge extent by selection of suitable secondary amine or mixture ofsecondary amines. Thus, for example, the dieneophile-functionalizedepoxy-amine adduct will comprise more dieneophile functionality permolecule if dialkanol amine is employed than if dialkylamine isemployed. This assumes, of course, that near stoichiometric amounts ofdieneophile functional mono-isocyanate reactant is employed in reactionwith the polyhydroxy functional epoxy-amine adduct. In general, agreater degree of dieneophile-functionalization (assuming acorresponding degree of diene-functionalization of the second essentialcomponent of the composition of the invention, that is thediene-functionalized polyisocyanate oligomer) will result in a curedcoating having a greater degree of crosslinking with correspondingphysical properties. While it will be within the ability of thoseskilled in the art in view of this disclosure to select secondary aminessuitable to generate a composition of the invention well adapted to aparticular application, it has been found that diethanolamine providesgenerally superior coatings and, as mentioned above, is generally mostpreferred. If less than stoichiometric amount of dieneophile functionalmono-isocyanate reactant is employed and/or if mixed secondary aminesare employed in reaction with the polyhydroxy epoxy-amine reactant, thena mixed reaction product will result which will, in general, function ina manner consistent with the foregoing description.

According to one embodiment of the invention, combinations of primaryand secondary amines can be employed with lower molecular weightpolyepoxides to increase the molecular weight of the epoxy-aminereaction product. However, secondary mono-amines are preferred, withdiethanolamine being most preferred.

A class of preferred hydroxy functional amine reactant includes those ofthe general formula: ##STR2## wherein R and R' are independentlystraight or branched chain monovalent aliphatic moieties of up to about10 carbons each, providing that at least one and preferably both R andR' is substituted by hydroxy on a primary carbon atom that is notadjacent to any amino nitrogen. R and R' can also form part of a ringcompound, such as a six membered ring. More preferably, R and R' areindependently alkyl and desirably up to 7 carbons each, even moredesirably up to 4 carbons each.

The polyepoxide and amine reactants are reacted at conditions that allowopening of the epoxy ring by amino nitrogen and provide a gel-freereaction product. The reaction of the epoxy functionality with secondaryamine can be expected to yield tertiary amino groups, whereas reactionwith primary amines can be expected to yield secondary amino groupswhich may undergo further reaction with an unreacted epoxy functionalityof the same or more probably of another polyepoxide molecule, resultingin chain extension.

Suitable reaction conditions and techniques are well known to theskilled of the art and will be apparent from the present disclosure.Thus, for example, the reaction medium preferably comprises non-aqueousmedium that may be of diverse but preferably polar character and servesto maintain contact of reactants, control reaction speed, maintaindesirable viscosity and other functions well known in the art. Thus,suitable solvents and diluents for the reaction medium include aromaticand aliphatic hydrocarbons, halides, ethers, ketones such as methylamylketone, n-amyl ether, xylene, oxygenated solvents such as cellosolves,for example butyl Cellosolve acetate, hexyl Cellosolve acetate and thelike, carbitols, for example carbitol acetate and the like, includingmixtures of these.

Elevated reaction temperatures may be employed to facilitate reactionbetween the polyepoxide reactant and the amine reactant and the reactionmay be conducted stepwise. The reactants are used preferably instoichiometric amounts. That is, it is preferred that sufficientsecondary amine reactant be used to react substantially all epoxyfunctionality of the polyepoxide reactant. More specifically, forexample, about 0.9-1.0 equivalent secondary amine functionality isreacted with about 1 to 1.1 equivalent epoxide functionality to yieldpolyhydroxy epoxy-amine adduct which is substantially free of unreactedepoxy functionality. More specifically, the polyhydroxy epoxy-amineadduct reaction product should contain less than 20% of the originalunreacted epoxy groups, more desirably less than about 10% and mostpreferably less than about 5% unreacted epoxy groups, based on thenumber originally present.

The dieneophile-functionalized epoxy amine adduct of the crosslinkablecomposition of the invention is the reaction product of the abovedescribed polyhydroxy epoxy-amine reactant with dieneophile functionalmono-isocyanate reactant. That is, the polyhydroxy epoxy-amine adduct isdieneophile-functionalized by reacting same with adieneophile-functional mono-isocyanate. Suitable dieneophile-functionalisocyanates are readily prepared employing readily available reactantsaccording to methods apparent to the skilled of the art in view of thepresent disclosure. In general, mono-diene-functional mono-isocyanatereactants are preferred in view of their ease of preparation and mostpreferred are those of formula O═C═N--R--B, wherein R is a bivalenthydrocarbon linking moiety which is substantially unreactive withisocyanate functionality and with substituent B, and B is a dieneophilemoiety reactive at elevated cure temperature with the aforesaid dienefunctionality of the diene-functionalized polyisocyanate oligomer. Thedieneophile moiety B is preferably of molecular weight about 30-200.Preferred dieneophile moieties include those according to formulas I-Ato I-H: ##STR3## or the like, wherein X⁰ is ##STR4## or the like,wherein R¹ is hydrogen, straight, branched or cyclo alkyl, aryl,arylalkyl or the like, and each R² is the same or different and each ishydrogen, hydroxy, carboxy, straight, branched or cyclo-alkyl, arylarylalkyl, or the like, each alkyl, aryl and arylalkyl moiety of R¹ andR² being unsubstituted or mono- or poly-hydroxy substituted or mono- orpoly-amino substituted; X¹, each X² and X⁸ are the same or different andeach is hydrogen, hydroxy, carboxy, amino, straight, branched orcyclo-alkyl, aryl, arylalkyl, cyano, nitro or the like, each alkyl, aryland arylalkyl moiety of X¹, X² and X⁸ being unsubstituted or mono- orpoly-hydroxy substituted or mono- or poly-carboxy substituted or mono-or poly-amino substituted; or X¹ and X⁸ together are --(CX²)_(n) --wherein n is an integer from about 3 to about 7, preferably about 3 to4; X⁶ is unsubstituted, or mono- or poly-hydroxy substituted or mono- orpoly-carboxy substituted or mono- or poly-amino substitutedalkanyl-ylidene of 2 or 3 carbons; and each X⁷ is the same or differentand each is a covalent bond, --O--, ##STR5## or the like. According toone most preferred embodiment, the dieneophile moiety B is: ##STR6##

One group of preferred dieneophile functional mono-isocyanate reactantsincludes the reaction products of one molar equivalent of suitablediisocyanate with one molar equivalent of dieneophile reactant selectedpreferably from the group consisting of monohydroxy functionaldieneophile reactants, monoamino functional dieneophile reactants andlike mono- and poly-dieneophile functional reactants having a singlefunctionality substantially reactive with the diisocyanate reactant, ora compatible mixture of any of them. Exemplary preferred dieneophilefunctional reactants include those of molecular weight about 30-500 suchas monohydroxy or monoamino or like isocyanate-reactive ene reactants,for example, methylolmaleimide, hydroxypropyl-methacrylate, allylalcohol, allyl amine, hydroxyethyl-methacrylate, hydroxyethylacrylateand the like and a compatible mixture of any of them. Also suitable forreaction are poly-dieneophile functional reactants, of which many arereadily prepared employing commercially available reactants according tomethods apparent to the skilled of the art in view of the presentdisclosure. A polydieneophile reactant may be preferred, for example,where the rate of reaction is relatively slow between the particulardiene and dieneophile functionality of the crosslinkable composition, toimprove the cure response of the composition.

Suitable organic diisocyanate reactants are readily commerciallyavailable and include many known to the skilled of the art such as, forexample, phenylene diisocyanates, toluene diisocyanates, isophoronediisocyanates, diisocyanatoalkane wherein the alkylene moiety has,preferably, from about three to about ten carbons, for example, hexanediisocyanate, or the like or a compatible mixture of any of them. Mostpreferably the organic diisocyanate has a molecular weight less thanabout 250. If corrosion resistance is of primary concern in the curedcoating, for example in the case of an automotive vehicle primer ortopcoat, it may be preferred to use an aliphatic diisocyanate, forexample, isophorone diisocyanate, 1,6-hexane diisocyanate and the like.Aromatic diisocyanates provide suitable coatings, however, and may bepreferred in view of their lower cost.

The dieneophile reactant and the diisocyanate reactant can be reactedaccording to well known techniques. Accordingly, approximately one molarequivalent of the dieneophile reactant can be added to the diisocyanateunder reaction conditions. Well known techniques can be employed tomaximize the yield of the dieneophile functional mono-isocyanatereaction product, such as, for example, adding the dieneophile reactantslowly to an excess of the organic diisocyanate under reactionconditions.

The dieneophile-functionalized epoxy-amine adduct component of thecrosslinkable composition of the invention is the reaction product ofdieneophile functional mono-isocyanate reactant with the above describedpolyhydroxy epoxy-amine reactant. The reactants are used preferably instoichimetric amount. That is, preferably sufficient dieneophilefunctional mono-isocyanate reactant is employed to react substantiallyall hydroxy functionality of the polyhydroxy epoxy-amine reactant. Thereaction product, that is, the dieneophile-functionalized epoxy-amineadduct, comprises, on average, at least about two dieneophile moietiesper molecule and preferably substantially no hydroxy functionality. Eachdieneophile moiety will be available for reaction with a diene moiety ofthe diene-functionalized polyisocyanate oligomer of the compositionduring curing at elevated temperature. More preferably, thedieneophile-functionalized epoxy-amine adduct will provide, on average,about three or more, such as about 3-20 dieneophile moieties permolecule.

According to an alternate embodiment of the invention, substantiallyless than all hydroxy groups of the polyhydroxy epoxy-amine are reacted.The resulting mixed reaction product would introduce hydroxy groups intothe crosslinkable composition of the invention. In this embodiment, thecrosslinkable composition could advantageously further comprisessuitable crosslinking agent reactive with each hydroxy groups. Numeroussuch crosslinking agents are well known to the skilled of the art andinclude, for example, any of a variety of aminoplast crosslinkingagents, for example, partially alkylated melamines (melaminesformaldehyde resins modified by alcohols), for example, partiallymethylated melamines and butylated melamines, polyalkyl ethers of thepolymethylol melamines, for example, hexamethoxy methylmelamine; ureaformaldehyde condensate modified by alcohol, for example,paraformaldehyde and trioxane; polymethylol compounds of hexamethylenediurea; adipic acid dimethylol amide and methylol ether thereof;tetramethylolhydrazodicarbonamide; polymethylol compounds ofpolycaprolactam and methylol ethers thereof; and the like or compatiblemixtures of any of them. Other suitable crosslinking agents will beapparent to the skilled of the art in view of the present disclosure.Butylated melamines are preferred since they are readily commerciallyavailable, and provide suitable crosslinking reactivity with theepoxy-amine adduct of the invention.

Diene-Functionalized Polyisocyanate Oligomer

This second essential component of the crosslinkable compositions of theinvention is the reaction product of a polyisocyanate reactant with adiene-functionalized reactant. Preferably the diene-functionalizedreactant has a single isocyanate-reactive functionality per molecule andthe polyisocyanate reactant has number average isocyanate functionalityof at least about 3 and most preferably is a triisocyanate. Suitablepolyisocyanate reactants will be apparent to the skilled of the art inview of the present disclosure and includes many which are commerciallyavailable or are readily prepared employing commercially availablereactants according to methods known to the skilled of the art. Thosepolyisocyanate reactants which are preferred will depend, in part, uponthe intended application of the crosslinkable composition in which thediene-functional polyisocyanate oligomer is to be used. Thus, forexample, for solvent-based coating compositions intended for applicationby spraying onto a substrate, (described further below), especially forso-called high-solids solvent-based coating compositions, the viscosityof the composition should be relatively low and, therefore, thepolyisocyanate is preferably of lower molecular weight, preferably ofnumber average molecular weight about 300-1000. Exemplary suchpolyisocyanates include for example, the reaction product of polyol,such as trimethylol propane and the like, with sufficient excess organicdiisocyanate, such as toluene diisocyanate and the like, to reactsubstantially all hydroxy functionality of the polyol. Also suitable isthe copolymerization reaction product of isocyanatefunctionalizedacrylic or methacrylic monomer with suitable additional reactivemonomers to form an acrylic copolymer having pendant isocyanatefunctionality. Suitable such additional reactive monomer includes, forexample, styrene monomer, acrylic acid, methacrylic acid, acrylatemonomers such as alkylacrylates and alkylmethacrylates, wherein thealkyl moiety is perferably of about 1-20 carbons, and the like and acompatible mixture of any of them. Suitable commercially availablepolyisocyanate include, for example, Desmodur E-21 (trademark), MondurHC (trademark), Desmodur N-75 (trademark), Desmodur N-100 (trademark),each of which is available from Mobay Chemical Co., Pittsburgh, Pa.,U.S.A., and the like or a compatiable mixture of any of them. Forcrosslinkable compositions of the invention intended for use in cathodicelectrocoating compositions, further described below, viscosity can beconsiderably higher and the polyisocyanate is preferably of highermolecular weight. Suitable such polyisocyanates include those namedabove and also, for example, the reaction product of an excess of theabove-listed triisocyanate materials with difunctional linkingcompounds, for example diamines, diols and the like, of which many areknown to the skilled of the art, or a compatible mixture of any of them.A preferred commercially available polyisocyanate is Desmodur L 2291A(trademark), a triisocyanate available from Mobay Chemical Corporation,Pittsburgh, Pa., U.S.A.

The polyisocyanate is reacted with suitable diene reactant, of whichmany will be apparent to the skilled of the art in view of the presentdisclosure. Numerous suitable diene reactants are commercially availableor are readily prepared employing commercially available reactantsaccording to methods known to the skilled of the art. Suitable dienereactants include, for example, monohydroxy functional diene reactants,monoamine functional diene reactants and like diene reactants having asingle functionality substantially reactive with isocyanatefunctionality. Those diene reactants which are preferred will depend, inpart, upon the intended application of the crosslinkable composition inwhich the diene functional polyisocyanate oligomer is to be used. Thus,for example, if the crosslinkable composition is intended for use in asolvent-based high-solids content sprayable coating composition, thediene reactant is preferably a monohydroxy diene, since these have beenfound to provide composition of somewhat lower viscosity. Monohydroxydiene reactants are also generally less expensive than correspondingmonoamine diene reactants. Where optimal corrosion resistance is aprimary consideration, however, monoamine diene reactant may bepreferred, since the urea linkage formed by reaction of the aminefunctionality with the isocyanate functionality will generally be morehighly alkali resistant than the corresponding urethane linkage.

In general, preferred diene reactants are mono-dienes, including mostpreferably those of formula M-R'-A, wherein M is hydroxy, amino, or likemono-functionality reactive with isocyanate, R' is a bivalenthydrocarbon linking moiety which is substantially unreactive withisocyanate functionality and with substituent A, and A is a dienemoiety, a monovalent olefinic moiety having 1,3-conjugated double bondsaccording to formula II: ##STR7## wherein X⁰ is as described above forformula I-A to I-H; X¹, each X², X³, X⁴ and X⁵ are the same or differentand each is hydrogen, hydroxy, carboxy, amino, straight, branched orcyclo-alkyl, aryl, arylakyl, cyano, nitro, or the like, or X¹ and X⁵together are alkylene, --O--, --NR¹ -- wherein R¹ is as defined above,or like divalent group (resulting in a cyclic diene moiety), each alkyl,aryl, arylalkyl and alkylene moiety of X¹, X², X³, X⁴ and X⁵ beingunsubstituted or mono-, or poly-hydroxy substituted or mono- orpoly-carboxy substituted or mono- or poly-amino substituted. Accordingto one most preferred embodiment of the invention, the diene moiety Ais: ##STR8##

One group of preferred diene-functionalized polyisocyanate oligomersincludes the reaction product of one molar equivalent of suitablepolyisocyanate with one molar equivalent of diene reactant selectedpreferably from the group consisting of monohydroxy functional dienereactants, monoamino functional diene reactants and like mono- andpoly-diene functional reactants having a single functionalitysubstantially reactive with the polyisocyanate reactant, or a compatiblemixture of any such diene functional reactants. Exemplary preferreddiene functional reactants include those of molecular weight about50-500 such as furfuryl alcohol, furfuryl amine,2-hydroxymethyl-1,3-butadiene, 2-aminomethyl-1,3-butadiene and the like.Also suitable for reaction with the polyisocyanate reactant aremonohydroxy, monoamino and like isocyanate reactive polydiene-functionalreactants, of which many are known to the skilled of the art and whichare commercially available or readily prepared employing commerciallyavailable reactants according to methods known to the skilled of theart. A polydiene reactant may be preferred where the rate of reaction isrelatively slow between the particular diene and dieneophilefunctionality of the crosslinkable composition, to improve the cureresponse of the composition.

The diene functional reactant and the polyisocyanate reactant can bereacted according to well known techniques. The molar equivalent ratioof polyisocyanate reactant to diene functional reactant should be suchas to ensure that substantially all isocyanate functionality is reacted.A significant amount of unreacted diene reactant in the finalcrosslinkable composition should also be avoided, since the dienefunctionality thereof would compete with the diene functionality of thediene-functionalized polyisocyanate oligomer for reaction with thedieneophile functionality of the dieneophile-functionalized epoxy-amineadduct. Preferably polyisocyanate reactant and diene reactant arereacted in molar equivalent ratio of about 1:1 to about 1:1.1.

The dieneophile-functionalized epoxy-amine adduct and thediene-functionalized polyisocyanate oligomer are employed in thecrosslinkable composition of the invention, preferably, in approximatelystoichiometric amount. That is, it is preferred that one molarequivalent weight of the former be employed together with about onemolar equivalent weight of the latter. In general, these two componentscan be used in relative amounts of about 1:0.8 to about 1.1.2 molarequivalent weights, respectively. If either or both of these componentscomprise unreacted hydroxy functionality, then crosslinking agent can beused up to near stoichiometric amount, that is, in amount up to thatsufficient to react substantially all such hydroxy functionality, toimprove cure response of the composition. If an aminoplast crosslinkingagent is employed, then it may be advantageous in certain embodiments orfor certain applications to include in the composition any of a varietyof compatible catalysts known to the skilled of the art to catalyze thecrosslinking reaction, for example, paratoluenesulfonic acid, phosphoricacid, phenol acid phosphate, butyl maleate and the like or a compatiblemixture of any of them. In addition, a flow control agent, for example,polybutylacrylate; a wetting agent, for example, silicone; pigments; apigment dispersent; and/or a corrosion inhibitor, for example, chromatepigment, several of all of which are known to the skilled of the art,may be employed in the coating compositions of the invention.

Di- and polyhydroxy compounds of diverse character may be employed alsoin the composition of the invention to modify the properties of thecomposition (i.e. the properties prior to or following cure) as well asto act as solvent, including reactive solvent, for solubilizing theself-crosslinkable epoxy-amine adduct. Thus, for example, thesecompounds may impart increased flexibility or reduce cratering inspray-applied cured films comprising the self-crosslinkable epoxy-amineadduct. A preferred class of hydroxy compounds includes aliphaticdihydroxy compounds, especially glycols and glycol ethers of the formulaHO(C_(a) H_(2a) O)_(x) -(C_(b) H_(2b) O)_(y) H wherein a, b, x and y areindependent integers and a and b are from 2 to 6 and x and y are from0-10 with the sum of x and y being 10. Examples include ethylene glycol,dipropylene glycol, and 1,6-hexanediol. Another class of glycolsincludes hydroxy terminated polybutadienes, hydrogenated bis-phenol-A,such hydroxy compounds being of generally hydrophobic character andnumber averagemolecular weights of preferably about 100-5000. Higherboiling solvents (e.g. boiling point above about 180° C., for example190°-250°) that are of polar character may tend to interact with theresinous components of crosslinking composition and thereby allow highersolids content. If such hydroxy functional compounds are included in thecomposition of the invention, then crosslinking agent reactive withhydroxy functionality, such as described above, should be employed,preferably in stoichiometric amount.

As noted above, pigments may be used in the primer compositions of theinvention in accordance with known techniques. Pigments are employedmost typically, for example, to enhance the efficacy of compositionsemployed as coating compositions over corrosion-susceptible substrates.Chromate pigments, in particular, have been used to enhance corrosionprotection. It is, however, a significant advantage of the presentinvention that chromate pigments need not be employed in compositionsemployed as such coating compositions over corrosion susceptiblesubstrates. Cured coating of the invention are highly alkali resistantand provide excellent corrosion protection even without chromatepigments. Such pigments and others can be employed, however, and may bedesirable for aesthetic purposes. Exemplary pigments include titaniumdioxide, silica, carbon black, and barytes and are employed typically atpigment:binder weight ratios of about 40:60 to about 60:40.

While not wishing to be bound by theory, it is presently understood thatduring the curing process at elevated temperature, the dienefunctionality and the dieneophile functionality react with each otherthrough Diels Adler cycloaddition chemistry. Taking the dieneophilefunctionality to be ene functionality for purposes of illustration, itis presently understood that the ene/diene reaction results in theformation of a cyclic six membered ring: ##STR9## In like manner, thecycloaddition reaction of a cyclic diene with an ene moiety yields abicyclic carbon-carbon linkage: ##STR10## Such Diels Alder reactionshave been studied and several parameters have been identified whichaffect reactivity. Exemplary such work is found in P. Wasserman, "DielsAlder Reactions", Elsevier Publishing Co., New York, 1965, which isincorporated herein by reference. Such parameters are found to includemost notably the selection of the substituent groups on the diene anddieneophile moieties, steric hindrance at the reaction site andmolecular orientation. In this regard, it is one characterizing aspectof the present invention that the substituent groups on the dienefunctionality of the diene-functionalized polyisocyanate oligomer and onthe dieneophile functionality of the dieneophile-functionalizedepoxy-amine adduct employed in the compositions of the invention areselected to provide the desired degree of reactivity, that is, cureresponse. In particular, the degree of reactivity is increased by enemoiety substitution groups which, in net effect, are electronwithdrawing, that is, which increase the electron affinity of the enefunctionality double bond. Thus, for example, reactivity is increased byelectron withdrawing ene substitution groups such as nitro, cyano, ester(i.e., ##STR11## nitrile, carbonyl, straight, branched or cyclo alkyl oralkylene, arylene, aralkylene, --O--, --NR--, --S-- and the like.Similarly, it will be understood by the skilled of the art in view ofthe present disclosure, that the shelf stability of the composition isenhanced by ene moiety substitution groups which, in net effort, areelectron donating, that is, which decrease the electron affinity of theene functionality double bond. Thus, shelf life is increased bysubstituent groups such as, for example, amine and ether linkages,sulfoxide, sulfone, urethane and the like.

It will be within the ability of those skilled in the art, in view ofthe present disclosure, to select dieneophile substituent groups whichprovide, in net effect, the desired compromise between shelf stabilityand reactivity. It generally is preferred that no electron donatinggroup(s) be substituted directly on either carbon of the enefunctionality double bond, nor on any adjacent or next adjacent atom. Incertain applications, however, particularly where extended shelf life isof paramount importance, such electron donating groups can be tolerated,more preferably in conjunction with electron withdrawing group(s) ofgreater effect, and with sufficient reaction catalyst, higher curetemperatures, longer cure periods, or a combination thereof.

In view of the present disclosure, it will be appreciated by the skilledof the art that in accordance with the foregoing discussion,compositions of the invention are rendered more reactive by dienefunctionality wherein the diene moiety substitution groups are electrondonating in net effect, that is, wherein the electron affinity of thediene double bonds is increased. Likewise, electron withdrawing groupson the diene moiety increase the shelf stability of the composition. Itgenerally is preferred that no electron withdrawing group(s) besubstituted directly on any carbon of either diene functionality doublebond, nor on any adjacent or next adjacent atom. As noted above,however, in certain applications a composition of the invention mayrequire extended shelf life or for some other reason call for ortolerate diene-functionalized polyisocyanate oligomers comprisingelectron withdrawing substitution groups on the diene moiety.

APPLICATIONS

As noted above, the crosslinkable composition of the invention is usefulin a variety of applications including, especially, as a coatingcomposition to provide an aesthetic and/or protective film on asubstrate. In particular, the crosslinkable composition of the inventioncan be formulated into a variety of primer formulations including bothaqueous primer formulations and non-aqueous primer formulations. Suchprimers can be used as coatings for bare or treated steels (e.g.,conversion coated with phosphates) as well as for guide coats overpreviously deposited primers applied, for example, by electrodeposition.Conventional modifying ingredients can be used in such primerformulations including, for example, flow control agents, pigments,pigment dispersents, thixotropes, anti-cratering aids, photo stabilizersand the like, as indicated above.

SOLVENT BASED PRIMERS

Coating compositions comprising diene-functionalized polyisocyanateoligomer and dieneophile-functionalized epoxy-amine adduct can bedispersed in organic solvent and applied to a substrate, for example aferrous metal substrate, according to well known techniques such as byspray, curtain, dip and other such coating methods. For solvent-basedcoatings to be applied by spray application methods, thediene-functionalized polyisocyanate oligomer is preferably of numberaverage molecular weight about 450-2000, and thedieneophile-functionalized epoxy-amine adduct is preferably of numberaverage molecular weight about 800-2000. It will be within the abilityof those skilled in the art to determine a suitable solvent and amountof same for a given coating composition of the invention, for a givenapplication. It will be understood that any solvent allowed to remain inthe cured coating should be inert so as to avoid adverse effects uponthe cured coating or upon another coating used in conjunction with it,during the curing process or thereafter. Preferably the cured coating issubstantially free of solvent. Sufficient solvent is used to reduce theviscosity of the coating composition to a level suitable for applicationto the substrate in the desired manner. Thus, for example, for acomposition to be used as a spray-applied primer coating composition, itis preferred that sufficient solvent be used to reduce the viscosity ofthe coating composition to about 25-35 seconds, No. 4 Ford Cup at 27° C.(80° F.).

Solvent based coating compositions according to the invention are curedby heating same to a sufficient temperature for a sufficient time todrive off the solvent and to cause reaction of the diene functionalitywith the dieneophile functionality and of the hydroxyl functionality, ifany, with the crosslinking agent, if any. Thus, for example, a solventbased coating composition comprising the crosslinkable composition ofthe invention according to preferred embodiments described above,applied by spray techniques to the surface of an automotive vehicle bodypanel as a primer coat would be cured by heating to a temperature ofabout 150°-210° C. for approximately 15-30 minutes.

WATER BASED COATING COMPOSITIONS

The crosslinkable composition of the present invention can be formulatedinto water based coating compositions. Accordingly, thedieneophile-functionalized epoxy-amine adduct is at least partiallyneutralized by acid, preferably weak organic acid such as formic,acetic, which is generally preferred, lactic, butryric acid or the likeor a compatible mixture of any of them. Additional suitable neutralizingacids (often referred to as "solubilizing acid") are known to theskilled of the art and will be apparent in view of the presentdisclosure. The at least partially neutralizeddieneophile-functionalized epoxy-amine adduct and thediene-functionalized polyisocyanate oligomer are dispersed into water,preferably de-ionized water for use either in spray application methods,flow coating, etc. or electrodeposition methods. Cured coatingsresulting from such methods are found to provide exceptionally good flowcharacteristics resulting in smooth and otherwise aesthetically superiorfilms having exceptionally good solvent and humidity resistance. Thecured coatings were also found to be highly alkali resistant and thus,to provide exceptionally good corrosion protection to the underlyingsubstrate. Water based coating compositions according to the inventioncan be employed in spray application techniques. Thus, for example, theycan be employed as a spray-applied primer coat for automotive vehiclebody panels.

Coating compositions of the invention wherein the crosslinkablecomposition is applied to the surface of a substrate byelectrodeposition technique is a particularly preferred embodiment ofthe invention. According to this embodiment, the crosslinkable coatingcomposition, as described above, is at least partially, and preferablysubstantially totally neutralized with solubilizing acid and thereafterdispersed into de-ionized water to a concentration of about 5-25 weightpercent, more preferably about 10-15 weight percent. The resulting waterbased composition is adapted for use as a cathodic electrocoatcomposition. That is, the coating comprising the crosslinkable resinsand crosslinking agent, catalysts etc., if any, will deposit upon theworkpiece acting as the cathode according to known electrodepositionsystems and techniques. For coating compositions adapted for cathodicelectrodeposition, the dieneophile-functionalized epoxy-amine resin ispreferably of number average molecular weight about 2000-7000, and thediene-functionalized polyisocyanate oligomer is preferably of numberaverage molecular weight about 2000-7000.

Cathodic electrodeposition according to the present invention is donepreferably at voltages of about 1-500 volts, more preferably about200-400 volts. Subsequent to electrodeposition, the coating on thesubstrate is heated to above about 130° C., more preferably about150°-210° C., for a time sufficient to effect the diene/dieneophilereaction and to drive off substantially the entire aqueous solventcontent of the coating. Employing a crosslinkable composition accordingto preferred embodiments described above, the coating will besubstantially completely cured following baking at about 158° C. forabout 30 minutes. In general, it will be within the ability of thoseskilled in the art to select suitable electrodeposition voltage andbaking temperatures and like process parameters in view of theparticular application involved.

Such aqueous solvent based coating compositions can comprise a mixtureof water and water compatible solvent and diluents such as ethyleneglycols and alkylated glycols, for example oxygenated solvents such asCellosolves and carbitols and the like or a compatible mixture of any ofthem. For use as spray primers, for example, such water based coatingcompositions can be formulated with high levels of water, for example,greater than about 10%, such as about 30-50% by weight, and yet curewithin conventional conditions such as, for example, at temperaturesabove about 130° C., more preferably about 150°-210° C., in about 30minutes or less, e.g. about 15-30 minutes according to preferredembodiments. Obviously, the particular time and temperatures necessaryto effect curing of the coating will depend upon the particularepoxy-amine adducts employed in the coating composition and will dependupon the thickness of the coating, the use of catalysts, and likeparameters familiar to the skilled of the art.

The invention will be further understood by referring to the followingdetailed examples. It should be understood that these examples arepresented by way of illustration and not by way of limitation. Unlessotherwise specified, all references to "parts" are intended to meanparts by weight.

EXAMPLE I

This example, illustrates the preparation of a polyhydroxy epoxy-aminereactant from higher molecular weight Bisphenol A-epichlorohydrin epoxyresin and dialkanolamine. To a solution of 93 g (0.1 molar equivalentweight) of Epon 1004¹ (trademark) in 93 g butoxy ethyl acetate was added10.5 (0.1 mole) diethanol amine. The reaction mixture was heated to70°-80° C. and maintained at that temperature for four hours. Thepolyhydroxy epoxy-amine reaction product, shown to be epoxide free uponIR analysis by absence of 910 cm⁻¹ peak, was cooled to room temperatureand stored.

EXAMPLE II

This example illustrates the preparation of a polyhydroxy epoxy-aminereactant from higher molecular weight Bispheniol A-epichlorohydrin epoxyresin and monoalkanolamine. Following the procedures of Example I 7.4 g(0.1 mole) of N-methyl ethanol amine is reacted with 93 g of Epon 1004¹(trademark) in 93 g butoxy ethyl acetate. The epoxide free polyhydroxyepoxy-amine reaction product is cooled to room temperature and stored.

EXAMPLE III

This example illustrates the preparation of a polyhydroxy epoxy-aminereactant from a lower molecular weight Bisphenol A-epichlorohydrin epoxyresin and dialkanolamine. Following the procedures of Example I, 10.5 g(0.1 mole) diethanol amine is reacted with 19.0 g (0.1 molar equivalentweight) Epon 828² (trademark) in 93 g butoxy ethyl acetate. The epoxidefree polyhydroxy epoxy-amine reaction product is cooled to roomtemperature and stored.

EXAMPLE IV

This example illustrates the preparation of polyhydroxy epoxy-aminereactant from low molecular weight aliphatic diepoxide anddialkanolamine. Following the procedures of Example I, 10.5 g (0.1 mole)diethanol amine is reacted with 20.2 g (0.1 molar equivalent weight)1,4-butane diol diglycidyl ether. The epoxide free polyhydroxyepoxy-amine reaction product is cooled to room temperature and stored.

EXAMPLE V

This example illustrates the preparation of an ester-bearing polyhydroxycyclic aliphatic epoxy-amine reactant. Following the procedures ofExample I, 126 g (0.1 mole) Araldite Cy 179³ (trademark) is reacted with10.5 g dialkanolamine in 130 g methyl amyl ketone. The epoxide freepolyhydroxy epoxy-amine reaction product is cooled to room temperatureand stored.

EXAMPLE VI

This example illustrates the preparation of dieneophile functionalmono-isocyanate reactant having a relatively less reactive dieneophilemoiety. To a solution comprising 222 g (1.0 mole) isophoronediisocyanate and 1 g dibutyl tin dilaurate in 100 g methyl ethyl ketoneheated to 60°-80° C. was added a solution of 70.0 g (1.0 mole) allylalcohol in 73 g methyl ethyl ketone. The reaction mixture was maintainedat 60°-80° C. for one hour following the addition. The dieneophilefunctional mono-isocyanate reaction product was cooled to roomtemperature and stored.

EXAMPLE VII

This example illustrates the preparation of a dieneophile functionalmono-isocyanate reactant having a moderately reactive dieneophilemoiety.

Step A: preparation of maleate. To a solution of 19.6 g (0.2 mole)maleic anhydride in 13.1 g methyl ethyl ketone was added 6.4 g methanoland 100 mg. triethylamine. The reaction was heated to 60°-80° C. andmaintained at that temperature for about one hour and then usedimmediately in Step B.

Step B: preparation of substituted maleate havig the structure:##STR12## To the entire reaction mixture of Step A, at about 60° C., wasadded 26 g (0.2 mole) butyl glycidyl ether and 0.15 g Cordova AMC-2⁴(trademark) catalyst. The reaction mixture was again heated for aboutsix hours until all epoxide functionality had reacted as shown by IRanalysis.

Step C: preparation of diene functional mono-isocyanate. The procedureof Example VI was followed using the entire contents of the reactionmixture of Step B with 44 g (0.2 mole) isophorone diisocyanate anddibutyl tin dilaurate as catalyst. The dieneophile functionalmono-isocyanate reaction product was cooled to room temperature andstored.

EXAMPLE VIII

This example illustrates the preparation of dieneophile functionalmono-isocyanate having relatively highly reactive dieneophile moiety.Following the procedures of Example VI, 127 g (1.0 mole)methylolmaleimide was reacted with 222 g (1.0 mole) isophoronediisocyanate. The dieneophile functional mono-isocyanate was cooled toroom temperature and stored.

EXAMPLE IX

This example illustrates the preparation of apolydieneophile-functionalized epoxy-amine adduct. The entirepolyhydroxy epoxy-amine product of Example I was combined with 324.5 gof the dieneophile functional mono-isocyanate prepared in Example VIII.The reaction mixture was heated to 60°-80° C. under an argon atmosphereuntil substantially all isocyanate functionality was reacted. Theresulting polydieneophile-functionalized epoxy-amine adduct was cooledand stored for use in a coating composition according to the presentinvention.

EXAMPLE X

The example illustrates the preparation of polydiene-functionalizedpolyisocyanate oligomer suitable for use in crosslinkable compositionsaccording to the present invention. To a solution of 390 g (one N═C═Omolar equivalent) of Desmodur L-2291A⁵ and 1 g bidutyl tin dilaurate in140 g methyl ethyl ketone was added dropwise at a rate sufficient tomaintain the reaction temperature at 60°-80° C., 196 g (1 mole) furfurylalcohol, a cyclic diene. Following addition of the furfuryl alcohol, thereaction temperature was maintained at 60°-80° C. until substantiallyall isocyanate functionality had reacted, as determined by IR analysis.The polydiene-functionalized polyisocyanate was cooled and stored atroom temperature.

EXAMPLE XI

The example illustrates the preparation ofpolydieneophile-functionalized polyisocyanate oligomer suitable for usein crosslinkable composition according to the present invention.Following the procedure of Example X, 84 g (1 mole) of2-hydroxymethyl-1,3-butadiene, an acyclic diene, is reacted with thetriisocyanate. The reaction temperature is maintained at 30°-45° C. Thereaction product is cooled and stored at room temperature.

EXAMPLE XII

This example illustrates a typical pigment package suitable for use in acoating composition according to the present invention.

    ______________________________________                                        Pigment Package                                                               ______________________________________                                        Aluminum silicate                                                                              7.0 g                                                        White lead       5.6 g                                                        Carbon Black     1.0 g                                                        ______________________________________                                    

EXAMPLE XIII

This example illustrates the preparation of a solvent-based primercoating composition according to the present invention. One half of theentire polydieneophile-functionalized epoxy-amine adduct product ofExample IX is combined with the pigment package of Example XII and theresulting mill base is ground until a Hegman Gauge reading of at least 7is obtained. The remaining portion of the polydiene-functionalizedepoxy-amine adduct is added and the resulting mill base is combined withthe entire polydieneophile-functionalized polyisocyanate oligomerproduct of Example XI. The composition is thoroughly mixed, itsviscosity is reduced with methyl ethyl ketone to 30-40 sec., No. 4 FordCup (27° C.), and it is filtered. The resulting solvent-basedcomposition is suitable for use by spray application methods as a primercoat for corrosion protection of an underlying substrate.

EXAMPLE XIV

This example illustrates the use of a crosslinkable composition ofmatter according to the present invention. The solvent-based primercomposition of Example XIII is applied by spray technique to bare,unpolished steel panels and cured by baking at 180° C. for 30 minutes.The cured coating provides good resistance to corrosion of the steelsubstrate.

EXAMPLE XV

This example illustrates the preparation of an aqueous solvent-basedcathodic electrodepositable coating composition according to the presentinvention. The solvent present with the polydiene-functionalizedpolyisocyanate oligomer prepared according to Example XI is replaced bycoupling solvent to facilitate dispersion into aqueous medium suitablefor electrodeposition. Accordingly, the polydiene-functionalizedpolyisocyanate oligomer of Example XI is combined with 50. g of butylcellosolve acetate and the resulting mixture is distilled until a solidscontent of 80% by weight is obtained. The solvent present with thepolydieneophile-functionalized epoxy-amine adduct prepared according toExample IX is replaced by coupling solvent to facilitate dispersion intoaqueous medium suitable for electrodeposition. Accordingly, thepolydieneophile-functionalized epoxy-amine adduct of Example IX iscombined with 50. g of butyl Cellosolve acetate and the resultingmixture is distilled until a solids content of 80% by weight isobtained. One half of the resulting polydieneophile-functionalizedepoxy-amine solution is combined with the pigment package of Example XIIand the resulting mill base is ground until a Hegman Gauge reading of atleast 7 is obtained. The remaining portion of thepolydieneophile-functionalized epoxy-amine adduct solution is added andthe resulting mill base is combined with the aforesaidpolydiene-functionalized polyisocyanate oligomer solution. The mixtureis partially neutralized with 60 g glacial acetic acid and is slowlydispersed into 1500 g of deionized water. The resulting aqueousformulation is filtered. The aqueous solvent-based composition issuitable for use in cathodic electrodeposition coating operations todeposit a primer coat for corrosion protection of a suitable substrate.

EXAMPLE XVI

This example illustrates the use of a crosslinkable composition ofmatter according to the present invention. The aqueous solvent-basedcomposition of Example XV is applied by cathodic electrodepositionmethods, at 100-300 volts, to bare, unpolished steel panels. Thecomposition is cured by baking the coated panels at 180° C. for 30minutes. The cured coating is found to provide good resistance tocorrosion of the underlying substrate.

In view of this disclosure, many modifications of this invention will beapparent to those skilled in the art. It is intended that all suchapparent modifications fall within the true scope of this invention andbe included within the terms of the appended claims.

INDUSTRIAL APPLICABILITY

It will be apparent from the foregoing that this invention hasindustrial applicability as a coating composition, especially as acathodic electrodeposition primer coating composition for sheet stelland the like used in automotive vehicles, household appliances and thelike, and other applications where the coating composition desirably hasexcellent storage stability and the cured coating desirably providesexcellent humidity and solvent resistance to protect the substrateagainst corrosion, wear and the like.

What is claimed is:
 1. A crosslinkable composition of matter, whichcomposition comprises:A. substantially gel-freedieneophile-functionalized epoxy-amine adduct, comprising the reactionproduct of (i) polyhydroxy functional epoxy-amine reactant comprisingthe reaction product of polyepoxy reactant having an average of at leastabout 2 epoxy groups per molecule with secondary amine reactant having atotal of less than about 20 carbons per amino nitrogen, wherein eachhydroxy group, if any, of the secondary amine is removed at least 1carbon from each amino nitrogen, with (ii) dieneophile functionalmono-isocyanate reactant; and B. substantially gel-free, substantiallyisocyanate-free diene-functionalized polyisocyanate oligomer havingnumber average diene functionality of at least about three, comprisingthe reaction product of (i) polyisocyanate reactant with (ii)isocyanate-reactive diene functional reactant, wherein thepolyisocyanate reactant and the diene functional reactant are in molarequivalent ratio of one to at least about one, respectively.
 2. Thecrosslinkable composition of matter of claim 1, wherein the polyepoxyreactant for said polyhydroxy functional epoxy-amine reactant isselected from the group consisting of Bisphenol A-epichlorohydrin epoxyresin, Novolak epoxy resin, aliphatic epoxy resin and a compatiblemixture of any of them.
 3. The crosslinkable composition of matter ofclaim 1, wherein the polyepoxy reactant for said polyhydroxy functionalepoxy-amine reactant has number average molecular weight about 700-8000.4. The crosslinkable composition of matter of claim 1, wherein saidsecondary amine reactant for said polyhydroxy functional epoxy-aminereactant is selected from the group consisting of dialkylamine,dialkanolamine, N-alkylaniline and a compatible mixture of any of them,wherein each alkyl moiety and each alkanol moiety has from one to aboutten carbons.
 5. The crosslinkable composition of matter of claim 3,wherein said secondary amine reactant for said polyhydroxy functionalepoxy-amine reactant consists essentially of diethanolamine.
 6. Thecrosslinkable composition of matter of claim 1, wherein said dieneophilefunctional mono-isocyanate reactant comprises the reaction product of(a) diisocyanate reactant in approximately one-to-one molar ratio with(b) dieneophile reactant selected from the group consisting ofmonohydroxy functional dieneophile reactant, monoamino functionaldieneophile reactant and a compatible mixture of any of them.
 7. Thecrosslinkable composition of matter of claim 6, wherein saiddiisocyanate reactant is selected from the group consisting of phenylenediisocyanate, toluene diisocyanate, isophorone diisocyanate,diisocyanatoalkane wherein the alkyl moiety has about three to about tencarbons and a compatible mixture of any of them.
 8. The crosslinkablecomposition of matter of claim 6, wherein said dieneophile reactant isselected from the group consisting of methylolmaleimide,hydroxypropyl-methacrylate, allyl alcohol, allyl amine,hydroxyethyl-methacrylate, hydroxyethylacrylate, and a compatiblemixture of any of them.
 9. The crosslinkable composition of matter ofclaim 1, wherein said diene functional reactant is selected from thegroup consisting of monohydroxy functional diene reactant, monoaminofunctional diene reactant and a compatible mixture of any of them. 10.The crosslinkable composition of matter of claim 9, wherein said dienefunctional reactant is selected from the group consisting of furfurylalcohol, furfuryl amine, 2-hydroxymethyl-1,3-butadiene,2-aminomethyl-1,3-butadiene and a compatible mixture of any of them. 11.The crosslinkable composition of matter of claim 1, wherein saidpolyisocyanate reactant consists essentially of triisocyanate.
 12. Thecrosslinkable composition of matter of claim 1, wherein saidpolyisocyanate reactant is seolected from the group consisting of thereaction product of polyol with sufficient excess organic diisocyanateto react substantially all hydroxy functionality of the polyol; acryliccompolymer reaction product of isocyanato-functionalized acrylic ormethacrylic monomer with reactive monomer selected from the groupconsisting of styrene monomer, acrylic acid, methacrylic acid, acrylatemonomer, alkylacrylate monomer, methacrylate monomer, alkylmethacrylatemonomer, wherein the alkyl moiety of said alkylacrylate andalkylmethacrylate monomer is from 1 to about 20 carbons, and acompatible mixture of any of them.
 13. The crosslinkable composition ofmatter according to claim 1, wherein said dieneophile-functionalizedepoxy-amine adduct bears hydroxy functionality, said composition furthercomprising crosslinking agent substantially reactive with hydroxyfunctionality.
 14. The crosslinkable composition of matter according toclaim 1 adapted for use in coating compositions that retard corrosion ofcorrosion susceptible substrates, further comprising organic solvent,wherein said diene-functionalized polyisocyanate oligomer is of numberaverage molecular weight about 450-2000, and saiddieneophile-functionalized epoxy-amine adduct is of number averagemolecular weight about 800-2000.
 15. A crosslinkable composition ofmatter adapted for use in electrodeposition of coatings on a substrate,which coatings are heat curable, which composition comprises:A.substantially gel-free substantially isocyanate-freediene-functionalized polyisocyanate oligomer having number average dienefunctionality of at least about three, comprising the reaction productof:(i) polyisocyanate reactant, with (ii) diene functional reactantwherein said polyisocyanate reactant and said diene functional reactantare reacted in molar equivalent ratio of one to at least about one,respectively; and B. substantially gel-free dieneophile-functionalizedepoxy-amine adduct, at least partially neutralized with solubilizingacid, which dieneophile-functionalized epoxy-amine adduct comprises thereaction product of:(i) polyhydroxy functional epoxy-amine reactantcomprising the reaction product of polyepoxy reactant having an averageof at least about 2 epoxy groups per molecule, with secondary aminereactant having a total of less than about 20 carbons per aminonitrogen, wherein each hydroxy group, if any, of the secondary amine isremoved at least 1 carbon from each amino nitrogen, with (ii)dieneophile functional mono-isocyanate reactant;which at least partiallyneutralized dieneophile-functionalized epoxy-amine adduct anddiene-functionalized polyisocyanate oligomer are dispersed together inaqueous solvent.
 16. The crosslinkable composition of matter of claim15, wherein said polyepoxy reactant for said polyhydroxy functionalepoxy-amine reactant has number average molecular weight about 700-8000.17. The crosslinkable composition of matter of claim 15, wherein saidsecondary amine reactant for said polyhydroxy functional epoxy-aminereactant is selected from the group consisting of dialkylamine,dialkanolamine, N-alkylaniline or a compatible mixture of any of them,wherein each alkyl moiety and each alkanol moiety has from one to aboutten carbons.
 18. The crosslinkable composition of matter of claim 15,wherein said secondary amine reactant for said polyhydroxy functionalepoxy-amine reactant consists essentially of diethanolamine.
 19. Thecrosslinkable composition of matter of claim 15, wherein saiddieneophile functional mono-isocyanate reactant comprises the reactionproduct of (a) diisocyanate reactant in approximately 1:1 molar ratiowith (b) dieneophile reactant selected from the group consisting ofmonohydroxy functional dieneophile reactant, monoamino functionaldieneophile reactant and a compatible mixture of any of them.
 20. Thecrosslinkable composition of matter of claim 19, wherein saiddiisocyanate reactant is selected from the group consisting of phenylenediisocyanate, toluene diisocyanate, isophorone diisocyanate,diisocyanatoalkane wherein the alkyl moiety has about three to about tencarbons and a compatible mixture of any of them.
 21. The crosslinkablecomposition of matter of claim 19, wherein said dieneophile reactant isselected from the group consisting of methylolmaleimide,hydroxypropyl-methacrylate, allyl alcohol, allyl amine,hydroxyethyl-methacrylate, hydroxyethylacrylate and a compatible mixtureof any of them.
 22. The crosslinkable composition of matter of claim 15,wherein said diene functional reactant is selected from the groupconsisting of monohydroxy functional diene reactant, monoaminofunctional diene reactant and a compatible mixture of any of them. 23.The crosslinkable composition of matter of claim 22, wherein said dienefunctional reactant is selected from the group consisting of furfurylalcohol, furfuryl amine, 2-hydroxymethyl-1,3-butadiene,2-aminomethyl-1,3-butadiene and the like and a compatible mixture of anyof them.
 24. The crosslinkable composition of matter of claim 15,wherein said polyisocyanate reactant consists essentially oftriisocyanate.
 25. The crosslinkable composition of matter of claim 15,wherein said polyisocyanate reactant is selected from the groupconsisting of the reaction product of polyol with sufficient excessorganic diisocyanate to react substantially all hydroxy functionality ofthe polyol; acrylic copolymer reaction product ofisocyanate-functionalized acrylic or methacrylic monomer with reactivemonomer selected from the group consisting of styrene monomer, acrylicacid, methacrylic acid, acrylate monomer, alkylacrylate monomer,methacrylate monomer, alkylmethacrylate monomer, wherein the alkylmoiety of said alkylacrylate and alkylmethacrylate monomer is from 1 toabout 20 carbons, and a compatible mixture of any of them.
 26. Thecrosslinkable composition of matter of claim 15, wherein saidsolubilizing acid is selected from the group consisting of acetic acid,lactic acid, formic acid, butyric acid and a compatible mixture of anyof them.
 27. The crosslinkable composition of matter of claim 15,wherein at least a portion of said dieneophile-functionalizedepoxy-amine adduct bears hydroxy functionality, said composition furthercomprising crosslinking agent substantially reactive with said hydroxyfunctionality.
 28. The crosslinkable composition of matter of claim 15,further comprising an organic coupling solvent miscible with water. 29.The crosslinkable composition of matter according to claim 15, whereinsaid diene-functionalized polyisocyanate oligomer is of number averagemolecular weight about 2000-7000, and said dieneophile-functionalizedepoxy-amine adduct is of number average molecular weight about2000-7000.
 30. A crosslinkable composition of matter adapted for use inelectrodeposition of coatings on a substrate, which coatings are heatcurable, which composition comprises:A. substantially gel-freesubstantially isocyanate-free diene-functionalized polyisocyanateoligomer of number average molecular weight about 2000-7000, comprisingthe reaction product of:(i) triisocyanate, with (ii) isocyanate-reactivediene functional reactant,wherein said triisocyanate and said dienefunctional reactant are reacted in molar equivalent ratio of one to atleast about one, respectively, said diene functional reactant beingselected from the group consisting of furfuryl amine,2-aminomethyl-1,3-butadiene and a compatible mixture of any of them; andB. substantially gel-free dieneophile-functionalized epoxy-amine adductof number average molecular weight about 2000-7000, at least partiallyneutralized with solubilizing acid selected from the group consisting ofacetic acid, lactic acid, formic acid, butyric acid and a compatiblemixture of any of them, which dieneophile functionalized epoxy-amineadduct comprises the reaction product of:(i) polyhydroxy functionalepoxy-amine reactant comprising the reaction product of polyepoxidereactant having an average of at least about two epoxy groups permolecule with secondary amine reactant selected from the groupconsisting of dialkanolamine wherein each alkanol moiety has one toabout three carbons; and (ii) dieneophile functional mono-isocyanatereactant comprising the reaction product of (a) diisocyanate reactantselected from the group consisting of phenylene diisocyanate, toluenediisocyanate, isophorone diisocyanate, diisocyanatoalkane wherein thealkyl moiety has about three to about ten carbons, and a compatiblemixture of any of them, with (b) dieneophile reactant selected from thegroup consisting of methylomaleimide, hydroxypropylmethacrylate, allylalcohol, allyl amine, hydroxyethyl-methacrylate, hydroxyethylacrylateand a compatible mixture of any of them;which at least partiallyneutralized dieneophile-functionalized epoxy-amine adduct anddiene-functionalized polyisocyanate oligomer are dispersed together inaqueous solvent.